Vertical shaft furnace system

ABSTRACT

A vertical shaft furnace in which the burden or charge is supported at the base of the furnace with an open annular space surrounding the charged material within the hearth, one or more angularly or tangentially disposed downwardly inclined tuyeres for introducing preheated air, with or without added fuel, into the annular space, a bypass line which connects with the base to vent the open annular space and thereby control the degree of heating and location of heating of the burden or charge according to its location within the vertical furnace, the bypass line including valve means for controlling the outlet flow through the bypass line in accordance with the prevailing conditions of the operations, an intermediate takeoff in the vertical shaft furnace for removing volatiles and gaseous byproducts at subatmospheric pressures for subsequent processing or treatment, and valved means for introducing fluxes or other additives into the annular space at the hearth on a controlled or metered continuous basis.

United States Patent [72] Inventor Kenneth W. Stookey Markle, Ind. [21]Appl. No. 855,516 g 22 Filed Se t. 5, 1969 [45] Patented Dec. 28, 1971[73] Assignee Torrax Systems, Inc.

North Tonawanda, N.Y. Continuation-impart of application Ser. No.531,244, Mar. 2, 1966, now abandoned and a continuation-in-part of 719,300, Mar. 25, 1968, now Patent No. 3,51 1,194. This application Sept.5, 1969, Ser. No. 85,516

[54] VERTICAL SHAFT FURNACE SYSTEM 10 Claims, 4 Drawing Figs.

[52] US. Cl 266/25, 266/31 [51] Int. Cl C21b 7/00 [50] Field of Search.266/25, 27, 28, 31, 41

[56] References Cited UNITED STATES PATENTS 485,392 11/1892 Koneman266/25 846,216 3/1907 Kemp 266/25 2,283,163 5/1942 Brassert et a1.266/25 Primary ExaminerGerald A. Dost Attorney-K. W. Brownell ABSTRACT:A vertical shaft furnace in which the burden or charge is supported atthe base of the furnace with an open annular space surrounding thecharged material within the hearth, one or more angularly ortangentially disposed downwardly inclined tuyeres for introducingpreheated air, with or without added fuel, into the annular space, abypass line which connects with the base to vent the open annular spaceand thereby control the degree of heating and location of heating of theburden or charge according to its location within the vertical furnace,the bypass line including valve means for controlling the outlet flowthrough the bypass line in accordance with the prevailing conditions ofthe operations, an intermediate takeoff in the vertical shaft furnacefor removing volatiles and gaseous byproducts at subatmosphericpressures for subsequent processing or treatment, and valved means forintroducing fluxes or other additives into the annular space at thehearth on a controlled or metered continuous basis.

PATENTED UEC28 m1 SHEET 1 [IF 2 FIG.I

INVENTOR. KENNETH W. STOOKEY PATENTEnniczsisn b 3.630.508

SHEET 2 OF 2 1 75 80 s5% I II 76 i:

\ V Ill 73 t 72 INVENTOR.

KEN NETH W. STOOKEY moi $5M VERTICAL SHAFT FURNACE SYSTEM Thisapplication is a continuation-in-part of my pending application Ser. No.53 l ,244 filed Mar. 2, 1966, now abandoned and of my pendingapplication Ser. No. 719,300 filed Mar. 25, 1968 now US. Pat. No. 3,51l,l94.

This invention relates to an improved process and apparatus in the fieldof metallurgical operations and more particularly to processes andapparatus for producing molten metals in vertical shaft-type furnacessuch as cupolas, blast furnaces and the like.

In the present invention 1 provide at the hearth zone of the furnace aninternal annular space so that blast air, or blast air in combinationwith some fuel such as a hydrocarbon gas, oil, coal, or the like, may beintroduced through the tuyeres and will have a circular flow path aroundthe furnace burden or charge. The blast air will exert a uniformpressure and penetration of the charge and have a subsequent uniformheating and chemical reaction with the charge.

The furnace is further featured by the provision of means at theintermediate portion of the vertical shaft for withdrawing of the hotgaseous products of combustion and volatiles at below atmosphericpressure for further treatment or processing as may be desired, and alsoa means for the continuous controlled or metered feeding of fluxes orother additives to the annular combustion space in the hearth so thatthey will be uniformly and effectively dispersed into the charge.

ln furnaces which are now in use blast air is directed along a generallyhorizontal plane and on the radials against the burden and this producesa cavitated zone or raceway directly in front of each tuyere and thenumber of tuyeres is spaced so that the raceways will approach anoverlapping relation with each other. As a result there is a scallopeddesign around the periphery of the burden as evidence of this lack ofuniformity of treatment of the charge. In order to subject the burden toan even approximate uniformity there must be a number of tuyeres whichare equally disposed around the furnace. The multiplicity of the tuyeresproduces an expensive item of construction and each is a source ofpotential trouble and is difficult both to maintain and operate. I findthat when hot blasts in the order of 1,500 to 2,000 F. are used there isno practical way to damper the airflow to achieve a uniformity of airdistribution or change in airflow through the various tuyeres should itbe found desirable.

it is one of the important objectives of the present invention toovercome these described problems by the use of an internal annuluswhich makes it possible to achieve better metallurgical operation with afewer number of tuyeres. Depending, of course, upon the diameter of thefurnace there may be as little as one tuyere; or in a larger furnace thesarn'e metallurgical effect can be achieved with as .few as two or threetuyeres. Whatever the number actually is, however, there can be asubstantial reduction over the number previously required thus achievingan economy in furnace construction and more uniform operation. Even whenthere is more than one tuyere used, the balanced flows through theindividual tuyeres are no longer as critical as it once was since theair and air pressure equalizes throughout the internal annulus toproduce a highly desired uniform treatment to the charge.

It is a further important object of the present invention to achieve abetter control of the heat in the slag and molten metal in the furnacewell. During the starting up of furnace or cupola operation the metalproduced is often too cold to use as a casting metal. It is the practiceeither to pig such metal or pour it into sand beds until the propermetal temperatures have been achieved for a suitable castingtemperature. The cool metal can be reclaimed by passing it again throughthe cupola but this is an item of cost which the present inventionproposes to eliminate.

In order to construct the annulus at the hearth zone of the furnace Iproduce a flaring of the hearth section, thus producing an annular spacewhich surrounds the charge in the furnace well. This annular space mayalso be provided with a suitably lined purge or vent line leading from apoint near the top of the annulus to atmosphere or into the furnace airpollution control system. The line shall be valved so that it can befully closed, fully opened or adjusted to any intermediate positionbetween the two extreme positions of full close and full open. Duringinitial heat up when fuels such as gas, oil or coal are introducedthrough the tuyeres along with the blast, the tuyeres serve somewhat onthe order of burners. At startup, when the furnace well together withthe slag and metal may be cold, the fuel and air are injected with thevent line open to some degree. Opening of the vent line permits therelease of heat within the hearth zone but also permits the spent hotgases to escape through the at least partially opened vent line.

It is conventional practice to pass the air and hot gases up the shaftand through the charge so that the charge becomes heated. By heating thecharge in this manner there is produced a melting which in turn causes adilution of cold material in the well and it is necessary to drain suchmixture from the well until proper temperatures have been achieved. Withthe use of a vent or bypass line, such hot gases do not pass through thecharge to any appreciable extent so that melting thereof is retardedwhile the hearth with its slag and metal are being heated to properoperating temperatures. It is, therefore, an important feature of thepresent invention to be able to manipulate a vent line by use of a ventvalve and consequently control the composition of the materials in thewell as well as the operating temperatures thereof during heat up andduring regular operation as well. In this way many important advantagescan be achieved in the way of improved operation of the furnace duringheat up as well as regular operation.

it is a still further objective of the present invention to increase therate of heat transfer and to improve the rate of chemical reactionbetween the slag and metal at their interface. It is the presentpractice to create such improved chemical reaction outside the furnacein a vessel known as a shaker ladle this is not a completelysatisfactory arrangement both by reason of the extra operation requiredand also by reason of the inherently slower reaction rate than isprovided by means of the present invention. What the present inventionproposes is a novel direction of hot blast air, or air and fuel whichstrikes or impinges against the surface of the slag at such an anglethat the kinetic energy of the blast impels the slag and metal in arotational sense around the channel formed between the furnace wall andthat portion of the burden which rests on the furnace bottom. Thedescribed rotation of materials is highly advantageous because of theturbulence produced between the metal and the slag at their interfaceand this is found to produce an accelerated rate of heat exchange andchemical reaction.

The described arrangement further makes it possible to add fluxingmaterials to the slag within the annular space either through thetuyeres or special openings and in this manner it is possible to correctquickly any undesirable metal condition. ln order to most effectivelyaccomplish the objective effectively achieving prompt control over theconditions of operation I provide means for so introducing additivesinto the hearth area that they are dispersed in the swirling flowcreated by the tuyere system and carried uniformly and quickly to allparts of the charge. This is done by providing means for introducing thedesired additives above the tuyeres on a continuous metered basis,desirably from a pressurized chamber. For example, in the event there iseither an excess of phosphorus or sulfur it is possible to make anaddition of lime, sodium hydroxide, or the like, directly into the slagby direct injection and such correction can be made almost immediately.Nonnally, the addition of such corrective materials to the top of thecharge at the top of the vertical shaft might take as many as two orthree hours to effect the necessary correction to the materials in thewell; introduction through doors provided in the sidewalls of the hearthdoes not provide immediate and effective disposal of the additive, anddoes not allow continuous metered feeding, when desired; the presentinvention, however, is such that time delays are reduced to a matter ofa few seconds and good dispersion is accomplished.

lOlOlb 0093 By means of the improved rotational and difiusion effectobtained by the unique agitation of the materials it is possible to addadditional heat and get more rapid chemical reactions to the materialswhile not unduly accelerating the melt rate of the conventional burden.

A further important feature of the present invention is that I can usecast iron chips and fines in such a way as to achieve their almostcomplete recovery in subsequent melting operations. NOrmally it was notpossible to return these materials to a cupola without briquetting andeven then large portions were found to be unsuitable for briquetting.Even where such expedients were used the briquettes were not normallystructurally strong enough to withstand handling consequently a largeportion of it was blown out of the stack thus being lost to the systemand also becoming a source of atmosphere pollution.

in the present invention, however, such materials can be introduced intothe annular space which is provided at the base of the hearth andmaterial losses are not experienced. Because of the extreme fineness ofthese materials they will quickly melt and become a useful product.Escape of any portion of the fines is prevented because in the processof starting up the stack they are quickly filtered out and captured bythe burden.

These added fine materials have a cooling effect at the hearth becauseof their high heat absorption and consequently it is possible to addappreciable heat at the hearth without increasing the temperature in thewell. These difficulties are successfully overcome by means of rotatingthe slag and metal and because of the further ability to use tuyere fuelwith the air to maintain proper well temperature. it has been previouslytried in conventional cupola operation to add fines and chips but thishas not been successful in the past because of the rapid cooling of thehearth and also because of the practical difficulty of evenlydistributing the fines through each tuyere. It is frequently the casethat these chips and fines are saturated with cutting oils and waterfrom machining operations and so must be briquetted before charging.When such oils were driven off as vapors by the furnace heat this merelyadded to air pollution problems; but in the present invention it is onlynecessary to remove the water content since the oils have a fuel valueand instead of being a nuisance are completely burned in the hearth zonein the present invention. With hearth injection on a controllable basisthe present invention can make valuable use thereof.

It is an important feature of the present invention that the annularspace at the hearth zone permits the addition of certain materials atthe hearth zone rather than through the stack. In this way, thecomposition of the output material can be more quickly and preciselycontrolled and variations in composition can be be more readily attainedthan when the material is charged through the stack. Moreover, the usuallosses which occur where certain alloys are charged through the stackwill not result. For example, where additions of ferrosilicon are madein conventional operation this is accompanied by substantial oxidationlosses and such losses are entirely circumvented in the presentinvention. The -50 percent loss which is normally encountered whenferrosilicon is charged through the stack because of oxidation to silicais entirely eliminated in the present invention. Furthermore,intermittent additions without effective dispersal through bottom doorshave led to lack of uniformity in the material being processed or losttime waiting for uniform distribution to take place. in the presentinvention where such alloy materials are added in the hearth on acontinuous metered basis directly into the tuyere stream, the necessaryheat to compensate for their cooling effect can readily be generated inorder to maintain the correct tapping temperature.

Another important feature of the present invention is that thecupola-type furnace can utilize pelletized ore, sintered ore andpartially reduced ore as a portion of the charge and in this respect,the cupola resembles in certain aspects and techniques a blast furnaceoperation. In the present invention, by means of the use of an annulusin which any of a combinaan a tion of fuels can be injected through thetuyeres and combusted with the release of heat, such gases becomeconverted by contact with the coke to carbon monoxide and hydrogen, thusgiving control of gases to be generated for the gaseous reduction phasewithin the shaft.

Another highly important feature is the provision of a takeoff manifoldor gas collection ring positioned at an intermediate location on thevertical shaft whereby the hot gasesof combustion and volatilesgenerated in the course of the operation are withdrawn from the stackand made available for further treatment or processing before release.This feature, for example, makes it possible to utilize in place of thehigh grade of metallurgical coke herefore deemed to be essential, muchless expensive coal which is coked or charred as it progressesdownwardly through the stack with the volatiles being removed at the gascollection ring.

The foregoing advantages are ones which directly proceed from the noveluse of an annulus at the base of the shaft in conjunction with the otherfeatures pointed out above and with such arrangement, it is possible touse in combination therewith the novel combination of tuyeres which areso constructed and directed as to achieve the necessary agitation at thebottom of the furnace between the slag and molten metal interface.

There is thus achieved an improved release of heat and penetration ofthe material within the charged column and as a result there is asubstantial improved uniformity over present furnace capabilities. Afurther advantage is the use of tuyere angle and fuel which can beinjected through the tuyeres in order to achieve circulation of slag andiron for promoting improved reaction between the two and also to controlwith greater precision and advantage the metal output of the furnace.

The above and other objects and features of the above invention willbecome apparent from a consideration of the following description whichproceeds with reference to the accompanying drawings wherein:

FIG. 1 is a section view taken through the base of a cupola, showing thetuyeres and bustle pipe together with continuous material feeding meansabove the tuyeres;

FIG. 2 is an enlarged section view showing the addition ofa valved lineproviding for the release of heat within the hearth zone and with acooling arrangement added therein;

FIG. 3 is a section view taken on line 3-3 of FIG. 1; and

Fig. 4 is a further embodiment showing how the base of the cupola may bemodified in a further embodiment of the invention.

Referring now to the drawings, and particularly FIG. 1, a cupoladesignated generally by reference numeral 10 serves as a vertical shaftfurnace adapted for the melting and refining of material such as zinc,iron, lead or the like. In the case of ferrous material I effect itsconversion into foundry grade iron or hot pig iron at the base thereof.The invention is not limited to production of cast iron for foundry use,this being only one of several different applications of the invention.One such may be the melting of steel scrap, with much reduced carbonpickup, for charging oxygen blown furnaces, electric furnaces, and thelike. The cupola, or vertical shaft, is a relatively inexpensive steelshell, refractory-lined structure, or it may be an unlined water-cooledsteel shell except for refractory lining in the hearth zone and well,having a top 12 and loaded at its top in any of various suitablemanners, as, for example, by skip hoist, buckets, belt conveyors, or thelike (not shown) all of which are encompassed within the presentinvention. There is charged to the cupola any of a combination of scrap,pig iron, iron oxides, alloys, etc. in whatever quantities are desiredand a mixture of such materials can then be combined with the flux andcoke or coal and raised to the upper end of the cupola for chargingtherein through a charge opening. At the bottom end 36 of the cupola isa bustle pipe 38 and a plurality of tuyeres 40 through which is injecteda mixture of air from line 42 and fuel from line 44, the two materialsbeing added in the desired ratio, then directed inwardly into the space70 converging on the well 43 and impinging against the burden 45 andslag 56 (FIG. 2). The ratio of the two materials can be regulated in bya suitable control valve structure (not shown) which can determine therate of inflow of the combustible combination as well as the ratio ofthe materials.

The tuyere openings 48 as indicated in FIG. 2 project slightlydownwardly toward the well 43 of the cupola. At the well 43 of thecupola is a recess 52 wherein is collected a layer of the metal and atap opening 54 is provided to effect release of the molten metal whichis generated within the recess 52. An overlying layer of slag 56 (FIG.2) may be removed through an emergency tap opening 58 or in conjunctionwith the metal through tap hole 54.

It should be noted, from FIGS. 1 and 2, that at the bottom end of thevertical shaft furnace a wall section 60 flares outwardly in the shapeof a frustum of a cone or it might be on the order of a hemisphere sothat as the burden descends, it takes support through a taperedfrustoconical portion Q55 which rests on the bottom portion 64 of well43, leaving an annular open space 70 (FIG. 2) wherein is injected theblast air or air with some hydrocarbon fuel. The air injected from line42 can be preheated or it can be ambient. The advantage of the presentinvention is that it enables the generation of much higher heat releasesthan was the case in prior art cupola operation. One of the reasons whyit is possible to generate higher heat release is that the burden moreefficiently absorbs the heat and consequently, the greater order of heathas less tendency to raise the temperature of the refractory brick whichforms the walls of the hearth zone. Consequently, higher heat releasesare attainable because the thermal destructive temperature point of thematerials of construction are not attained.

It should also be noted that the tuyeres are located so that they arenot touched by the metal, slag or the burden as in conventional cupolasand blast furnaces. A further direct consequence of the use of annularcombustion zone 70 is that fuel and combustion-supporting gases can mixand burn in this open space. Referring to FIGS. 3 and 4 the tuyeres aredisposed tangentially or at least angularly (or nonradially) and extenddownwardly at regularly spaced circumferential locations. One of theeffects of disposing the tuyere passages and openings as indicated inFIG. 3 is that there is produced a circumferential flow ofcombustion-supporting gases directed downwardly against the well of thecupola, effecting a substantial agitation and rotation of the melt andthereby effecting an improved heat exchange between the interface of theslag and metal and more efficiently serves to accelerate the refinementof the metals. The improved interfacial relationship because of thisrotation and agitation minimizes or eliminates the need for a subsequentshake ladle" operation.

Located in the upper wall 60 of the hearth is an opening or openings 71through which fluxes, or other additives or materials can be fed on acontinuous and controlled or metered basis through connecting conduit 72containing valve 73 and leading to a storage chamber 74 containing thematerial to be fed into the combustion area. The storage chamber 74 isdesirably normally maintained under a slightly positive or aboveatmospheric pressure to assure positive feed of the material into thefurnace. The chamber 74 is replenished as need be with material fromcharge hopper 75 through conduit 76 which is equipped with valve means77. The location of the openings 7] above the position of the tuyerescauses the infeed of material to be introduced into the swirling air orgas stream from the tuyeres and be carried to all parts of thecombustion area in widely dispersed condition so as to effect immediateand effective distribution and assimilation by the charge within thehearth. Such effective assimilation cannot be accomplished in acomparable way by the admission of materials to the chargeintermittently through doors provided in the hearth walls.

Referring to FIG. 2, there can be included with the cupola a stackhaving an outlet opening 8! controlled by a throttling butterfly valve80 with a power-actuated operator 82.

During the startup of operations the valve can be fully opened therebyproviding for greater access of flue gases outwardly through the stackthan upwardly through the burden 45. Consequently, the heat which isgenerated within chamber 70 is confined essentially to the bottom of thecupola. Since a minimum of the overhead burden is melted, the bottom ofthe cupola is not rapidly flooded with cool metal and slag. Since thecupola does not need to be tapped during the heatup period owing to thedesirable occurrence of flooding from the upflow of heat into theburden, under initial warmup conditions, there is not generated as muchscrap from tapping the openings 54 and 58, therefore less scrap isgenerated during the heatup.

lt frequently happens, in the cupola operation, that the cupola may beidle for a day or two at a time, or longer, and it is during therestarting of operation that there is a considerable generation ofscrap. with the present invention, because of the ability to confine theheat at the startup of cupola operation to the base, (and for allpractical purposes bypassing the burden through venting of the heatthrough the stack 78 with the valve 80 fully opened) such wastefuloperation is successfully avoided. As the cupola starts to resumeoperation, the valve 80 can be successfully throttled and eventually theoperator 82 effects full closing of the valve 80 and all of thecombustion gases travel upwardly through the chamber 70 through theburden under normal cupola operation and maximum thermal efficiency.

At an intermediate point of the vertical shaft portion of the furnace isa gas collection ring 85 from which a line 86 passes to convey the gasesof combustion and volatiles as desired for further treatment orprocessing. The line 86 contains a valve 87, and the valve 87 contains apressure control device 88 with suitable barometric control sensor inthe gas collection ring 85 to maintain a subatmospheric pressuresufficient to keep the uprising gases from the base of the gasifier fromexiting at the upper end of the stack and causing any portion of theoutflow to leave through the line 86. Device 88 has sensing outlets at89 to atmosphere and at 90 within the gas collection ring 85 and at 87within line 86. These signals are fed centrally to the device 88 whichhas a servo outlet leading to the valve 87 for maintaining the suitablevalve setting whereby pressure conditions are maintained such thatsubatmospheric pressure always exists at the upper ring end 85 to keepall of the gases flowing through line 86.

In operation, the cupola 10 is charged with whatever combination ofmaterials is desired, in the form of scrap, iron, ore or combinationsthereof together with the desired amount of flux and coke or coal. Suchmaterials, after having filled the cupola to the desired height, arethen, are then converted to the desired type of metal. It might benodular, malleable or something other than pig iron. At the start ofoperation, the valve 80 of the stack 78 is fully opened and the bustlepipe 38 receives a flow of heated air which may be combined with fueladded through line 44 and the desired ratio and the inflow suitablyregulated to the desired amount. The adjusted mixture is injectedthrough tuyere openings 48 into the annular chamber 70 where it effectsat uniform pressure a substantially uniform penetration of the burden 45and ascends within chamber 70. The high heat releases which areattainable by reason of the novel structure makes it possible to effectconversion of the scrap steel, ore, iron or combinations of suchmaterials at accelerated rates. Furthermore, it is possible to injectinto the chamber 70 quantities of fuel gas, oil and solid carbonaceousmaterials if so desired and in this way it is possible to replace aportion of the coke burden which, being substantially more expensive,makes the cupola operation of my invention inherently more economical.Also, I can add cast iron fines and chips, ferrosilicon, turnings, etc.directly through openings 71 thereby making it possible adjust thecomposition of the cupola output promptly within a closely regulatedrange with uniform dispersion and distribution throughout the hearthcharge. Also, there is no need to wait for an appreciable time to makesuch adjustments of composition and causing generation of scrap untilthe adjustments are made.

When the valve 80 is opened, all of the combustion gases, for allpractical purposes, are vented through the stack 78 and only anegligible part of the gases rise upwardly through the burden 45 so thatthe cold bottom of the cupola during the startup operation receivessubstantially all of the heat. The heat is confined to the bottom sincenone of the heat from the uprising gases passes through the burden;consequently, there is prevented any occurrence of flooding of too coolmaterials at the bottom of the cupola. The burden rests at the base 64and the high heats generated within chamber 70 are uniformly "seen" byit to the extent that the burden defines one side of the chamber 70.These higher heats make it possible to use burdens which are inclusiveof scrap and without causing injury to the refractory lining of thecupola, As the bottom of the cupola is heated, the valve 80 is graduallyclosed, throttling the outflow of combustion product and a portion ofthe combustion product starts to travel upwardly through the burden 45until such time as the cupola is ready to resume normal operation, atwhich point the valve 80 is fully closed and all of the combustion gasesrise upwardly through the cupola. A balance is effected which precludesthe possibility of flooding at the bottom of the cupola.

The openings 48 are disposed at an angle (FIG. 3) and downwardly asindicated in FIGS. 1 and 2 and the combined burner flows arecomplementary to produce a swirling action around the interior of thechamber 70, thus agitating the interface between the slag 56 and themolten pig iron at the base recess 52, more efficiently effectingrefinement and heating of the metal.

The presence of the chamber 70 also makes it possible to controllablydetermine the optimum fuel-to-air ratio and therefore both by reason ofthe higher temperature and the controlled tendency of the atmosphere toproduce a reducing atmosphere it is possible to control the compositionof the metal.

The positioning of the openings 71 above the tuyeres along with theassociated means for metering under pressure a continuous and controlledflow of additives to the hearth zone assures an effective dispersal andassimilation of the materials to the charge for a prompt and evencorrection or adjustment or maintenance of the desired conditions ofoperation and properties and composition of product.

The collection ring 85 permits the use of coal in place of moreexpensive coke and allows for utilization and recovery of any values,thermal or chemical, to be derived from further processing or treatmentof the effluent volatiles and gases of combustion by reason of theirremoval at this point.

it will therefore be seen that the present invention is usable and ishighly advantageous not only in increasing the scope of usable materialsin the production of metal, but also makes it possible to generatehigher temperatures and produce a metal of greater quality anduniformity of product.

Referring to FIG. 4 the base or bottom end 36 of the cupola instead ofhaving a frustoconical-shaped wall section 60, can be constructed with acurved or sector cross section in order to produce a space 70 which isboth annular and surrounds the bottom end of the burden as in theprevious embodiment (FIG. 2). The burden 65 rests on a bottom portion 64of base 43 the same as in the previous embodiment and in all otherrespects the operation is the same as previous.

Also, referring to FIGS. 1 and 2, the stack can be either water cooledor it can be refractory lined depending upon design requirements. in thecase of water cooling, there are usual spaced weirs and a flow of liquidcoolant which progresses downwardly abstracting heat and protecting theouter wall of the cupola.

What is intended in these embodiments is the use of an annular or othersuitable shaped opening in the well of the eupola which permits theuniform penetration of the burden by the heated combustion gasesproduced within the chambers and there is uniform penetration of heatinto the burden at the base of the cupola. Moreover, the open spacepermits the supplying of injectants to control the composition of theproduct and also, it further permits the use ofa bypass line to controlthe heat up when the cupola operation is first initiated. These variousadvantages are obtainable with each of the described embodiments. lt hasfurther been found that the cupola can be made more economical tooperate because of the elimination of occurrence of waste from coldtapping and the higher temperatures are obtainable well within thetemperature limitations of the refractory materials of which the cupolais constructed.

Although the present invention has been illustrated an described inconnection with a single example embodiment, it will be understood thatthis is illustrative of the invention and is by no means restrictivethereof. It is reasonably to be expected that those skilled in this artcan make numerous revisions and adaptations of the invention to suitindividual design requirements and it is intended that such revisionsand adaptations will be included within the scope of the followingclaims as equivalents of the invention.

lclaim:

1. A metallurgical furnace having a base, a vertical shaft portion andat the base thereof a large cross section hearth which defines an open,annular space completely surrounding the charged stock within thehearth, a plurality of tuyeres, one disposed at each of a plurality ofcircumferentially spaced intervals disposed at the base of said furnaceand inclined downwardly and directed angularly so that the respectiveoutflows are complementary in effecting both agitation and swirlingaction within the annular space surrounding the charged stock, bypassmeans for controllably throttling an outflow of gaseous combustionproduct from within said annular open space to regulate the distributionof heat between said space and the overhead burden within said furnace,means for directing a combustible flow into said open annular spacethrough said tuyeres, and means for adding materials to the annular openspace surrounding the charged stock to be dispersed by the blast fromthe tuyeres.

2. The furnace in accordance with claim 1 wherein the means for addingmaterials to said annular open space comprises an opening in said hearthwall positioned above the horizontal line of the tuyeres, a conduitconnecting said opening to a closed chamber, and valve means forcontrolling the rate of flow from said chamber to said opening.

3. The furnace in accordance with claim 2 wherein the chamber forfeeding material to the furnace hearth is pressurized.

4. The furnace in accordance with claim 1 including means intermediateof the top and bottom ends of the vertical shaft portion for withdrawingthe hot gases of combustion and generated volatiles.

5. The furnace in accordance with claim 4 in which the withdrawal meanson the vertical shaft comprises a collection ring surrounding saidshaft.

6. The furnace in accordance with claim 5 including means formaintaining a negative or subatmospheric pressure at said collectionring.

7. The furnace in accordance with claim 5 including control meansoperable to maintain a subatmospheric pressure sufficient to cause asubstantial portion of the outflow gases to flow through said collectionring.

8. A metallurgical furnace having a base, a vertical shaft portion andat the base thereof a large cross section hearth which defines an open,annular space completely surrounding the charged stock within thehearth, a plurality of tuyeres, one disposed at each of a plurality ofcircumferentially spaced intervals disposed at the base of said furnaceand inclined downwardly and directed angularly so that the respectiveoutflows are complementary in effecting both agitation and swirlingaction within the annular space surrounding the charged stock, bypassmeans for controllably throttling an outflow of gaseous combustionproduct from within said annular open space to regulate the distributionof heat between lOIOI6 0006 tion ring.

9. The furnace in accordance with claim 8 wherein the chamber forfeeding material to the furnace hearth is pressurized.

10. The furnace in accordance with claim 9 including control meansoperable to maintain a subatmospheric pressure sufficient to cause asubstantial portion of the outflow gases to flow through said collectionring.

# i l I it

1. A metallurgical furnace having a base, a vertical shaft portion andat the base thereof a large cross section hearth which defines an open,annular space completely surrounding the charged stock within thehearth, a plurality of tuyeres, one disposed at each of a plurality ofcircumferentially spaced intervals disposed at the base of said furnaceand inclined downwardly and directed angularly so that the respectiveoutflows are complementary in effecting both agitation and swirlingaction within the annular space surrounding the charged stock, bypassmeans for controllably throttling an outflow of gaseous combustionproduct from within said annular open space to regulate the distributionof heat between said space and the overhead burden within said furnace,means for directing a combustible flow into said open annular spacethrough said tuyeres, and means for adding materials to the annular openspace surrounding the charged stock to be dispersed by the blast fromthe tuyeres.
 2. The furnace in accordance with claim 1 wherein the meansfor adding materials to said annular open space comprises an opening insaid hearth wall positioned above the horizontal line of the tuyeres, aconduit connecting said opening to a closed chamber, and valve means forcontrolling the rate of flow from said chamber to said opening.
 3. Thefurnace in accordance with claim 2 wherein the chamber for feedingmaterial to the furnace hearth is pressurized.
 4. The furnace inaccordance with claim 1 including means intermediate of the top andbottom ends of the vertical shaft portion for withdrawing the hot gasesof combustion and generated volatiles.
 5. The furnace in accordance withclaim 4 in which the withdrawal means on the vertical shaft comprises acollection ring surrounding said shaft.
 6. The furnace in accordancewith claim 5 including means for maintaining a negative orsubatmospheric pressure at said collection ring.
 7. The furnace inaccordance with claim 5 including control means operable to maintain asubatmospheric pressure sufficient to cause a substantial portion of theoutflow gases to flow through said collection ring.
 8. A metallurgicalfurnace having a base, a vertical shaft portion and at the base thereofa large cross section hearth which defines an open, annular spacecompletely surrounding the charged stock within the hearth, a pluralityof tuyeres, one disposed at each of a plurality of circumferentiallyspaced intervals disposed at the base of said furnace and inclineddownwardly and directed angularly so that the respective outflows arecomplementary in effecting both agitation and swirling action within theannular space surrounding the charged stock, bypass means forcontrollably throttling an outflow of gaseous combustion product fromwithin said annular open space to regulate the distribution of heatbetween said space and the overhead burden within said furnace, meansfor directing a combustible flow into said opEn annular space throughsaid tuyeres, an opening in said hearth wall positioned above thehorizontal line of the tuyeres, a conduit connecting said opening to aclosed chamber, and valve means for controlling the rate of flow fromsaid chamber to said opening, a collection ring intermediate of the topand bottom ends of the vertical shaft portion for withdrawing the hotgases of combustion and generating volatiles, and means for maintaininga negative or subatmospheric pressure at said collection ring.
 9. Thefurnace in accordance with claim 8 wherein the chamber for feedingmaterial to the furnace hearth is pressurized.
 10. The furnace inaccordance with claim 9 including control means operable to maintain asubatmospheric pressure sufficient to cause a substantial portion of theoutflow gases to flow through said collection ring.